Add redirect_back functionality

[matthewmcgarvey]

Purpose

Fixes #1158

redirect_back allows an action to send the user back to where they made the request from. This is really useful in situations like submitting a lead form where the app might have it in several locations but the app doesn't need to take them anywhere in particular after they submit it. Rather than sending the user to a specific place after submitting the form, we can now send them back to where they originally submitted it.

This was largely taken from Rails. source

Sidenote

If you look at the Rails code, there is functionality around limiting Referer redirects in some situations using the allow_other_hosts named argument. If it is set to false then it will not redirect to a Referer header that has a different host than the request host. So, if the app is running at example.com, it will not redirect to a Referer header of differenturl.com when set to false. While this might be useful, I didn't want to copy it over just to copy it.

Description

Usage looks like:

class NewsletterSignupsCreate < BrowserAction
  post "/newsletter/signup" do
    # do the signup code
    redirect_back fallback: Home::Index
  end
end

It's important that the fallback is required because the Referer header is not guaranteed so we need to send the user somewhere.

Checklist

• - An issue already exists detailing the issue/or feature request that this PR fixes
• - All specs are formatted with crystal tool format spec src
• - Inline documentation has been added and/or updated
• - Lucky builds on docker with ./script/setup
• - All builds and specs pass on docker with ./script/test

[jwoertink]

This does look great. The only thing I'm wondering is redirect allows for a HTTP::Status to be passed... I'm wondering if we should also include a method overload for that....

[matthewmcgarvey]

@jwoertink Good catch, there are just sooo many overloads!

[jwoertink]

😂 yup, but this is awesome! I saw what you mean with the allow_other_hosts. I think it's a little wonky. For now let's just roll without that, and we can think about a nice way to handle something like that later if people want it.

[paulcsmith]

One tiny comment then LGTM! Thanks for tackling this!

[paulcsmith]

Looks great! Thank you 🎉